A barcode is an optical machine-readable representation of information. Devices for identifying or extracting information from barcodes are generally referred to as barcode readers (or barcode scanners). An image-based barcode reader includes a focusing lens for focusing illumination reflected from a field of view of the barcode reader onto a photo sensor array to capture an image of a barcode within the field of view. Once an image of a barcode has been captured by the photo sensor array, a processor operating a decoder processes the image and extracts the information contained in the barcode.
Imaging barcode readers are useful in that they are generally capable of reading barcodes printed on a substrate and displayed electronically on a display screen. Generally, when reading a barcode printed on a substrate, the barcode reader utilizes the barcode reader's illumination system to illuminate the substrate within the field of view such that the focusing lens focuses reflected illumination on the photo sensor array. Generally, when reading a barcode electronically displayed on a display screen the backlight illumination of the display screen is sufficient for the barcode reader to read the barcode and the focusing lens focuses illumination emitted by the backlight of the display screen onto the photo sensor array.
In many applications where barcode readers are used to collect data, the time at which a barcode is read is often recorded in association with the decoded data obtained from the barcode. Barcode readers which are useful in such applications often times have an internal real-time clock function which enables the barcode reader to maintain time and associate the time that a barcode is read with the decoded data obtained from the barcode.
A problem exists in that a barcode reader with a real-time clock function must periodically have the time value maintained by the clock set or reset. Such a requirement may exist, for example, if the clock is unable to maintain time when the barcode reader is powered off.